1. Technical Field
Embodiments of the present disclosure relate to semiconductor devices controlling a refresh cycle time and semiconductor systems including the same.
2. Related Art
Dynamic random access memory (DRAM) devices among semiconductor devices may lose data stored in their memory cells as time elapses even while their power supplies are applied to their memory cells, in contrast to static random access memory (SRAM) devices or flash memory devices. In order to prevent the data stored in the DRAM cells from being lost, the DRAM devices may have an operation for rewriting data from external systems in a certain period, which is called “a refresh operation”. Usually, such a refresh operation is carried out, in retention times that are inherent in memory cells of the DRAM devices, by activating word lines at least once or more, and sensing/amplifying data of the memory cells. The retention time is a time that data can be maintained without a refresh operation after being written into a memory cell.
The data retention time of the DRAM cell including a single transistor and a single storage capacitor may be very sensitive to temperature. Thus, it may be necessary to control operation conditions of internal circuit blocks of a semiconductor system according to variation of an internal temperature of a semiconductor device in the semiconductor system. Temperature sensors such as digital temperature sensor regulators (DTSRs), analog temperature sensor regulators (ATSRs) or temperature compensated self-refresh (TCSR) sensors have been widely used to control operation conditions of semiconductor devices such as DRAM devices according to variation of the internal temperature of the semiconductor systems.